feat(goals): v2 architecture — drop ledger, derive balance, add pledge

Reshape the goals feature to live on top of linked-account balances.
A goal's balance is now the live balance of every depository account
linked to it — no parallel ledger, no "log a contribution" step.

The "Add contribution" affordance is replaced by a 7-day GoalPledge
(kind: transfer | manual_save). GoalPledge::Reconciler matches incoming
Transactions (via Account::ProviderImportAdapter) and Valuations (via
Account::ReconciliationManager) against open pledges within ±5 days,
±$0.50, or ±1% — single hook covers every provider (Plaid, SimpleFIN,
Lunchflow, Enable Banking, Brex, IBKR, Kraken, SnapTrade) plus manual
balance edits. A 15-minute Sidekiq cron sweeps expired pledges.

Goal model: balance derived from linked_accounts.sum(&:balance), new
pace (90-day net non-transfer inflow), months_of_runway,
last_matched_pledge_*, pledge_action_label_key (the "I just
transferred…" vs "I just saved…" verb switch).

UI:
- Index gets a 3-card KPI strip (Contributed last 30d / Needs this
  month / On track) plus a pending-pledges callout.
- Show page swaps the "Add contribution" CTA for the pledge modal,
  replaces the contribution list with a pending-pledge banner, and
  rebuilds the funding widget into per-account rows with a 12-bucket
  weekly sparkline and last-30 inflow.
- Projection chart adds a required-line (dashed light from
  today → target) and a translucent pending-pledge bump at today's X.

Schema (3 migrations):
1. goal_pledges table with PG enums (goal_pledge_kind, goal_pledge_status),
   open-by-expiry index, and unique-when-not-null matched_transaction_id.
2. Drop goal_contributions.
3. Partial unique index on
   transactions ((extra -> 'goal' ->> 'pledge_id')) built CONCURRENTLY
   so it doesn't block prod.

After pulling: run bin/rails db:migrate, then commit the schema.rb sync
separately (or let CI regenerate).

Deferred to v1.1: allocation columns, contention/archived banners,
"why is this behind?" diagnostic, reallocate flow, refresh-sync +
Plaid throttle, unallocated-cash chip, joint-account approval,
goal_activities log, polymorphic matched_entry_id/type for manual
pledge audit.

test/models/assistant/function/create_goal_test.rb

@@ -35,21 +35,6 @@ class Assistant::Function::CreateGoalTest < ActiveSupport::TestCase
     end
   end
 
-  test "creates a goal with initial contribution" do
-    assert_difference -> { GoalContribution.count } => 1 do
-      @fn.call(
-        "name" => "Laptop fund",
-        "target_amount" => 2000,
-        "linked_account_names" => [ @depository.name ],
-        "initial_contribution" => { "amount" => 200, "source_account_name" => @depository.name }
-      )
-    end
-
-    contribution = GoalContribution.order(created_at: :desc).first
-    assert_equal "initial", contribution.source
-    assert_equal 200, contribution.amount.to_i
-  end
-
   test "soft error when name is missing" do
     result = @fn.call("target_amount" => 100, "linked_account_names" => [ @depository.name ])
     assert_equal false, result[:success]